Automotive fuel system polymeric seals are deformable components that are widely used in many different applications to make a pressure-tight joint between parts, and include radial seals and axial seals. In use, radial seals are compressed in a radial direction perpendicular to a seal centerline on radially inside and outside surfaces of the radial seal's cross section, whereas axial seals are compressed in an axial direction parallel to a seal centerline on axially opposed surfaces of the axial seal's cross section. Axial seals, in particular, are widely used to seal openings of containers.
For example, axial seals are often used to seal an opening in a fuel tank and are disposed in a flange-type joint between a mounting flange of a fuel delivery module and an outer surface of the fuel tank. Unfortunately, however, an axial seal may not provide a substantially permeation-free joint between the mounting flange and the fuel tank. More specifically, due to relatively high volatility, hydrocarbons quickly vaporize from liquid fuel in the fuel tank and may escape to the atmosphere through the flange-type joint, if it is not suitably sealed. In fact, volatile fuel vapors may permeate right through the axial seal itself, in an otherwise pressure-tight sealed joint.
To address such leakage, the California Air Resources Board (CARB) has adopted regulations requiring vehicles to operate with a combination of a Super Ultra Low Emission Level (SULEV) and zero evaporative emissions of fuel, constituting a Partial Zero Emission Vehicle (PZEV). Zero evaporative emissions means no gases may be emitted from the vehicle's fuel tank or other fuel delivery systems.
One approach to providing a permeation-free flange-type joint to comply with the PZEV regulations is to use a special low-permeation type of seal material to seal a joint. But such materials are typically cost prohibitive for many applications, are relatively hard and, thus, difficult to compress during assembly, and usually exhibit low elasticity at low temperature.